21145871 has 2 divisors, whose sum is σ = 21145872. Its totient is φ = 21145870.

The previous prime is 21145829. The next prime is 21145919. The reversal of 21145871 is 17854112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21145871 - 2¹⁰ = 21144847 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21145811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10572935 + 10572936.

It is an arithmetic number, because the mean of its divisors is an integer number (10572936).

Almost surely, 2^21145871 is an apocalyptic number.

21145871 is a deficient number, since it is larger than the sum of its proper divisors (1).

21145871 is an equidigital number, since it uses as much as digits as its factorization.

21145871 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2240, while the sum is 29.

The square root of 21145871 is about 4598.4639826794. The cubic root of 21145871 is about 276.5297490301.

Adding to 21145871 its reverse (17854112), we get a palindrome (38999983).

The spelling of 21145871 in words is "twenty-one million, one hundred forty-five thousand, eight hundred seventy-one".